#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<stdio.h>
int main()
{
    int arr[] = {1,2,3,4,5,6,7,8,9,10};
    int k = 0;
    scanf("%d",&k);
    int sz = sizeof (arr)/sizeof(arr[0]);
    int left = 0;
    int right = sz-1;
    while(left<=right)
    {
    int mid = (left+right)/2;
    if(arr[mid]<k)
    {
        left = mid+1;
    }
    else if(arr[mid]>k)
    {
        right = mid-1;
    }
    else
    {
        printf("找到了，下标是：%d\n",mid);
        break;    
    }


    }
    if(left>right)
    {
        printf("找不到了\n");
    }
    return 0;
    
}